topic Re: Macro Logic to find Palindromes in SAS Programming

Macro Logic to find Palindromes

lhsumdalum — Mon, 12 Mar 2018 14:30:22 GMT

Hi,

I need to identify all palindromes within a directory. I use a proc contents and proc sort to identify the datasets within a directory, like so:

proc contentss data = dPath._all_ out = dFiles (keep = memname);
run; 

proc sort data = dFiles nodupkey; 
by memname;
run;

I want to identify palindromes within this directory. As it stands, the macro parameter would take in a string and reverse it. However, I would like to do this for all rows/columns for any dataset. How would I adapt the following logic to work for all columns/rows in a dataset?

%macro palindrome (parameter = ?); 

%let string = %sysfunc(reverse(%sysfunc(compress([WHAT TO PUT HERE?],,sp);
%let reverse = %sysfunc(compress([WHAT TO PUT HERE?]);

%if %upcase(&string.) = %upcase(&reverse.)  %then %do;
ods output = "/palindrome"
%end;

Re: Macro Logic to find Palindromes

RW9 — Mon, 12 Mar 2018 14:39:58 GMT

And who told you that you need to use macro? All that does is generate Base SAS which is the programming language and Base SAS has this functionality:

data want;
  set have;
  if strip(reverse(string))=strip(string) then palindrome="Yes";
run;

Re: Macro Logic to find Palindromes

lhsumdalum — Mon, 12 Mar 2018 14:42:15 GMT

Thank you for the reply, I plan to use macros because I need to do this for all datasets within a directory. So, instead of the user inputting the string to check if there is a palindrome, I need that to be done dynamically, i.e. identify any palindromes within a dataset.

Re: Macro Logic to find Palindromes

RW9 — Mon, 12 Mar 2018 14:48:26 GMT

data _null_;
  set sashelp.vcolumn (where=(libname="WORK"));
  by memname;
  if first.memname then call execute('data '||strip(memname)||'; set '||strip(memname)||';');
  call execute('if strip(reverse('||strip(name)||'))=strip('||strip(name)||') then '||strip(name)||'_palindrome="Yes";');
  if last.memname then call execute(';run;');
run;

Will do the palindrome check for every variable in every dataset in the work library. If you just want one dataset, then update the the where clause to be:

(where=(libname="WORK" and memname="TMP"))

For example only does TMP in WORK library, upcase is important.